Consolidated Statements of Shareholders' Equity (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2019
Cash dividends declared
Common stock, dividend per share (in dollars per share)	$ 0.43	$ 0.43	$ 1.29	$ 1.29
Cumulative Effect, Period of Adoption, Adjustment
Cash dividends declared
Impact of new accounting guidance, net of tax					$ 1,170
Impact of new accounting guidance, tax					$ 288
Series B Preferred Stock
Cash dividends declared
Preferred stock, dividend per depositary share (in dollars per share)	9.06	9.98	27.44	36.44
Series C Preferred Stock
Cash dividends declared
Preferred stock, dividend per depositary share (in dollars per share)	8.70	$ 9.20	26.32	$ 43.99
Series D Preferred Stock
Cash dividends declared
Preferred stock, dividend per depositary share (in dollars per share)	$ 4.24		$ 4.24